London
(12.08.13) – The affair of the tumorous French rats rumbles on.

Readers may remember the claims made in September 2012 that female rats
fed GM-herbicide-tolerant maize in a two–year study developed large
mammary tumours almost always more often than and before controls, tumours
which were the direct result of being fed that GM-maize together with or
without traces of glyphosate, the controlling herbicide (1).

The paper generated a veritable storm of protest from a host of individual
scientists (2) as well as from many regulatory authorities and scientific
academies and societies around the world, including six academies within
France itself.

The criticisms focussed on two main defects of the original study: that
the strain of rats used tend spontaneously to develop tumours over a two-year
life span and that the statistical data and evidence in support of the original
authors’ conclusions were quite inadequate for the complexity and
many variable of the original study.

But the affair did cause ructions and many individuals, organisations and
media outlets jumped on a bandwagon from heaven to promote their particular
causes, oblivious or uncaring about what the evidence did or did not show.
It led a number of countries to ban the import of GM-products, at least,
as it turned out in some cases, temporarily (3). Indeed, the announcement
of the French study appears to have been planned with the objective of promoting
a maximum level of confusion. The advance results were given under embargo
to journalists who agreed that they would seek no other opinion and consult
no specialists in the field (who, it was no doubt feared, might –
indeed, as it turned out, would –take a critical view of the French
study). Such a restriction on journalists’ right of consultation is
very rare indeed, if not totally unheard of.

After the original embargo had expired, and critics had an opportunity to
express their view, there was near universal condemnation of the study objectives
and methodology as well as the claims made on the basis of the data presented.

But it was too good an opportunity for the opponents of GM-technology to
allow to fade away. So recently one group has attempted to use guidelines
issued by the European Food Safety Authority in a new allegation: that they
validate the long-term GM feeding studies which found serious health effects
from NK603 maize (4). Nine specific points were mentioned; in particular:

2. EFSA says the same strain of rat that was used in the 90-day study
on the GM food should be used in the longer study - thus vindicating Seralini's
use of the Sprague-Dawley rat, which Monsanto used in its 90-day study on
the same maize.

3. EFSA says animals should be fed ad libitum, which Seralini did, but
which critics complained made it impossible to measure individual food and
water consumption.

7. EFSA recommends a minimum of 10 animals per sex per group for the chronic
toxicity phase, the same number that Seralini used.

Alison Van Eenennaam, who actually knows about such matters, looked at the
EFSA guidelines to find they defer to the OECD guidelines which state that
“Young healthy adult animals of commonly used laboratory strains should
be employed. The combined chronic toxicity/carcinogenicity study should
be carried out in animals from the same strain and source as those used
in preliminary toxicity study(ies) of shorter duration, although, if animals
from this strain and source are known to present problems in achieving the
normally accepted criteria of survival for long-term studies (see Guidance
Document No. 116 (7)), consideration should be given to using a strain of
animal that has a acceptable survival rate for the long-term study.”
Dr. Van Eenennaam then looked at Guidance Document No. 116 (7), which basically
says “Importantly, in selecting a suitable rat strain for carcinogenicity
testing, test animals should be selected that are likely to survive for
the recommended duration of the study (see section 3.3.2). Britton et
al. (2004) reported that of the three rat strains studied (Harlan Hsd:Sprague-Dawley
SD, Harlan Wistar Hsd:BrlHan:WIST, Charles River Crl:CD), Harlan Wistar
strain survived in much greater numbers in 104-week carcinogenicity studies.
The improved survival rate, according to the authors, appeared to be independent
of body weight and food consumption and was reflected in the spontaneous
pathology profile. Other authors believe this phenomenon to be attributable
to a combination of obesity and genetic susceptibility and advocate dietary
restriction as a method of extending survival in long-term carcinogenicity
bioassays (Keenan, 1996).

The document continues: “An important aspect of the feeding regime
used in chronic toxicity and carcinogenicity is the recognized effect on
study outcome of feeding ad libitum. Traditionally, maximal growth
and reproduction have been used as criteria for the evaluation of laboratory
animal diets (NRC, 1995). However, evidence from a number of studies indicates
that restricting the caloric intake of laboratory animals may have beneficial
effects on life span, the incidence and severity of degenerative diseases,
and the onset and incidence of neoplasia (Weindruch and Walford, 1988; Yu,
1994; Keenan et al. 1997). Based on these results, allowing animals
to eat ad libitum to produce maximum growth and reproduction may
not be consistent with objectives of long-term toxicological and aging studies
(NRC, 1995). Overfeeding by ad libitum food consumption is generally
considered to be the most significant, uncontrolled variable affecting the
outcome of the current rodent bioassay, and in particular, the correlation
of food consumption, the resultant adult body weight and the 2-year survival
in Sprague-Dawley rats is highly significant. (Keenan et al., 1997).
However, it will probably take years to introduce dietary restriction into
national and international test guidelines for toxicity testing because
of concern that the delayed occurrence of, for example, cancer reflects
a decrease in the sensitivity of the carcinogenicity test in detecting the
carcinogenic potential of tested chemical and because the considerable database
on historical control is based on data from ad libitum feeding
studies (Meyer et al., 2003). Species and strain differences in
survival are discussed further in chapter 3.3.”

So Dr. Van Eenennaam was able to conclude that the EFSA document suggests
NOT using Sprague-Dawley rats for long term (104 week) feeding studies but
rather the Harlan Wistar strain, having 50/sex/treatment group or at least
65/sex/treatment group if using Sprague-Dawley due to their known poor survival,
and that ad libitum food consumption is known to be a highly significant
effector on cancer and decreased 2-year survival in Sprague-Dawley rats.

Thus, Dr. Van Eenennaam is not at all sure on what planet all that equates
to claims of vindication by EFSA.

Never mind, those particular points probably will not be raised again but
there were six others in the article and imagination can no doubt dream
up still more. They may be relevant or irrelevant to the French study or
to the comments that followed. It doesn’t matter: the objective is
always to muddy the waters, generate as much uncertainty as possible, waste
people’s time and try to get them so fed up with sterile arguments
that they will not respond to the next one.